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https://github.com/espressif/esp-idf.git
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729 lines
21 KiB
C
729 lines
21 KiB
C
/*
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* GCM block cipher, ESP DMA hardware accelerated version
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* Based on mbedTLS FIPS-197 compliant version.
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*
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* SPDX-FileCopyrightText: The Mbed TLS Contributors
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* SPDX-FileContributor: 2016-2022 Espressif Systems (Shanghai) CO LTD
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*/
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/*
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* The AES block cipher was designed by Vincent Rijmen and Joan Daemen.
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*
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* http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf
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* http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
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*/
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#include "soc/soc_caps.h"
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#if SOC_AES_SUPPORT_GCM
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#include "aes/esp_aes.h"
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#include "aes/esp_aes_gcm.h"
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#include "aes/esp_aes_internal.h"
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#include "hal/aes_hal.h"
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#include "esp_log.h"
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#include "mbedtls/aes.h"
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#include "esp_heap_caps.h"
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#include "soc/soc_memory_layout.h"
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#include "mbedtls/error.h"
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#include <string.h>
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#define ESP_PUT_BE64(a, val) \
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do { \
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*(uint64_t*)(a) = __builtin_bswap64( (uint64_t)(val) ); \
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} while (0)
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/* For simplicity limit the maxium amount of aad bytes to a single DMA descriptor
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This should cover all normal, e.g. mbedtls, use cases */
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#define ESP_AES_GCM_AAD_MAX_BYTES 4080
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static const char *TAG = "esp-aes-gcm";
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static void esp_gcm_ghash(esp_gcm_context *ctx, const unsigned char *x, size_t x_len, uint8_t *z);
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/*
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* Calculates the Initial Counter Block, J0
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* and copies to to the esp_gcm_context
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*/
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static void esp_gcm_derive_J0(esp_gcm_context *ctx)
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{
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uint8_t len_buf[16];
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memset(ctx->J0, 0, AES_BLOCK_BYTES);
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memset(len_buf, 0, AES_BLOCK_BYTES);
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/* If IV is 96 bits J0 = ( IV || 0^31 || 1 ) */
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if (ctx->iv_len == 12) {
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memcpy(ctx->J0, ctx->iv, ctx->iv_len);
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ctx->J0[AES_BLOCK_BYTES - 1] |= 1;
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} else {
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/* For IV != 96 bit, J0 = GHASH(IV || 0[s+64] || [len(IV)]64) */
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/* First calculate GHASH on IV */
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esp_gcm_ghash(ctx, ctx->iv, ctx->iv_len, ctx->J0);
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/* Next create 128 bit block which is equal to
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64 bit 0 + iv length truncated to 64 bits */
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ESP_PUT_BE64(len_buf + 8, ctx->iv_len * 8);
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/* Calculate GHASH on last block */
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esp_gcm_ghash(ctx, len_buf, 16, ctx->J0);
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}
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}
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/*
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* Increment J0 as per GCM spec, by applying the Standard Incrementing
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Function INC_32 to it.
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* j is the counter which needs to be incremented which is
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* copied to ctx->J0 after incrementing
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*/
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static void increment32_j0(esp_gcm_context *ctx, uint8_t *j)
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{
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uint8_t j_len = AES_BLOCK_BYTES;
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memcpy(j, ctx->J0, AES_BLOCK_BYTES);
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if (j) {
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for (uint32_t i = j_len; i > (j_len - 4); i--) {
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if (++j[i - 1] != 0) {
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break;
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}
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}
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memcpy(ctx->J0, j, AES_BLOCK_BYTES);
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}
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}
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/* Function to xor two data blocks */
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static void xor_data(uint8_t *d, const uint8_t *s)
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{
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for (int i = 0; i < AES_BLOCK_BYTES; i++) {
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d[i] ^= s[i];
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}
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}
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/*
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* 32-bit integer manipulation macros (big endian)
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*/
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#ifndef GET_UINT32_BE
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#define GET_UINT32_BE(n,b,i) \
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{ \
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(n) = ( (uint32_t) (b)[(i) ] << 24 ) \
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| ( (uint32_t) (b)[(i) + 1] << 16 ) \
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| ( (uint32_t) (b)[(i) + 2] << 8 ) \
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| ( (uint32_t) (b)[(i) + 3] ); \
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}
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#endif
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#ifndef PUT_UINT32_BE
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#define PUT_UINT32_BE(n,b,i) \
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{ \
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(b)[(i) ] = (unsigned char) ( (n) >> 24 ); \
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(b)[(i) + 1] = (unsigned char) ( (n) >> 16 ); \
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(b)[(i) + 2] = (unsigned char) ( (n) >> 8 ); \
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(b)[(i) + 3] = (unsigned char) ( (n) ); \
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}
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#endif
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/* Based on MbedTLS's implemenation
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*
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* Precompute small multiples of H, that is set
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* HH[i] || HL[i] = H times i,
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* where i is seen as a field element as in [MGV], ie high-order bits
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* correspond to low powers of P. The result is stored in the same way, that
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* is the high-order bit of HH corresponds to P^0 and the low-order bit of HL
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* corresponds to P^127.
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*/
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static int gcm_gen_table( esp_gcm_context *ctx )
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{
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int i, j;
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uint64_t hi, lo;
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uint64_t vl, vh;
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unsigned char *h;
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h = ctx->H;
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/* pack h as two 64-bits ints, big-endian */
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GET_UINT32_BE( hi, h, 0 );
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GET_UINT32_BE( lo, h, 4 );
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vh = (uint64_t) hi << 32 | lo;
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GET_UINT32_BE( hi, h, 8 );
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GET_UINT32_BE( lo, h, 12 );
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vl = (uint64_t) hi << 32 | lo;
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/* 8 = 1000 corresponds to 1 in GF(2^128) */
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ctx->HL[8] = vl;
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ctx->HH[8] = vh;
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/* 0 corresponds to 0 in GF(2^128) */
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ctx->HH[0] = 0;
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ctx->HL[0] = 0;
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for ( i = 4; i > 0; i >>= 1 ) {
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uint32_t T = ( vl & 1 ) * 0xe1000000U;
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vl = ( vh << 63 ) | ( vl >> 1 );
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vh = ( vh >> 1 ) ^ ( (uint64_t) T << 32);
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ctx->HL[i] = vl;
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ctx->HH[i] = vh;
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}
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for ( i = 2; i <= 8; i *= 2 ) {
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uint64_t *HiL = ctx->HL + i, *HiH = ctx->HH + i;
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vh = *HiH;
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vl = *HiL;
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for ( j = 1; j < i; j++ ) {
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HiH[j] = vh ^ ctx->HH[j];
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HiL[j] = vl ^ ctx->HL[j];
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}
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}
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return ( 0 );
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}
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/*
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* Shoup's method for multiplication use this table with
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* last4[x] = x times P^128
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* where x and last4[x] are seen as elements of GF(2^128) as in [MGV]
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*/
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static const uint64_t last4[16] = {
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0x0000, 0x1c20, 0x3840, 0x2460,
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0x7080, 0x6ca0, 0x48c0, 0x54e0,
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0xe100, 0xfd20, 0xd940, 0xc560,
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0x9180, 0x8da0, 0xa9c0, 0xb5e0
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};
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/* Based on MbedTLS's implemenation
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*
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* Sets output to x times H using the precomputed tables.
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* x and output are seen as elements of GF(2^128) as in [MGV].
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*/
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static void gcm_mult( esp_gcm_context *ctx, const unsigned char x[16],
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unsigned char output[16] )
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{
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int i = 0;
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unsigned char lo, hi, rem;
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uint64_t zh, zl;
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lo = x[15] & 0xf;
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zh = ctx->HH[lo];
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zl = ctx->HL[lo];
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for ( i = 15; i >= 0; i-- ) {
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lo = x[i] & 0xf;
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hi = x[i] >> 4;
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if ( i != 15 ) {
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rem = (unsigned char) zl & 0xf;
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zl = ( zh << 60 ) | ( zl >> 4 );
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zh = ( zh >> 4 );
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zh ^= (uint64_t) last4[rem] << 48;
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zh ^= ctx->HH[lo];
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zl ^= ctx->HL[lo];
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}
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rem = (unsigned char) zl & 0xf;
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zl = ( zh << 60 ) | ( zl >> 4 );
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zh = ( zh >> 4 );
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zh ^= (uint64_t) last4[rem] << 48;
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zh ^= ctx->HH[hi];
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zl ^= ctx->HL[hi];
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}
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PUT_UINT32_BE( zh >> 32, output, 0 );
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PUT_UINT32_BE( zh, output, 4 );
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PUT_UINT32_BE( zl >> 32, output, 8 );
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PUT_UINT32_BE( zl, output, 12 );
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}
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/* Update the key value in gcm context */
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int esp_aes_gcm_setkey( esp_gcm_context *ctx,
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mbedtls_cipher_id_t cipher,
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const unsigned char *key,
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unsigned int keybits )
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{
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#if !SOC_AES_SUPPORT_AES_192
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if (keybits == 192) {
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return MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED;
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}
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#endif
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if (keybits != 128 && keybits != 192 && keybits != 256) {
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return MBEDTLS_ERR_AES_INVALID_KEY_LENGTH;
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}
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ctx->aes_ctx.key_bytes = keybits / 8;
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memcpy(ctx->aes_ctx.key, key, ctx->aes_ctx.key_bytes);
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return ( 0 );
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}
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/* AES-GCM GHASH calculation z = GHASH(x) using h0 hash key
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*/
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static void esp_gcm_ghash(esp_gcm_context *ctx, const unsigned char *x, size_t x_len, uint8_t *z)
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{
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uint8_t tmp[AES_BLOCK_BYTES];
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memset(tmp, 0, AES_BLOCK_BYTES);
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/* GHASH(X) is calculated on input string which is multiple of 128 bits
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* If input string bit length is not multiple of 128 bits it needs to
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* be padded by 0
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*
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* Steps:
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* 1. Let X1, X2, ... , Xm-1, Xm denote the unique sequence of blocks such
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* that X = X1 || X2 || ... || Xm-1 || Xm.
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* 2. Let Y0 be the “zero block,” 0128.
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* 3. Fori=1,...,m,letYi =(Yi-1 ^ Xi)•H.
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* 4. Return Ym
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*/
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/* If input bit string is >= 128 bits, process full 128 bit blocks */
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while (x_len >= AES_BLOCK_BYTES) {
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xor_data(z, x);
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gcm_mult(ctx, z, z);
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x += AES_BLOCK_BYTES;
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x_len -= AES_BLOCK_BYTES;
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}
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/* If input bit string is not multiple of 128 create last 128 bit
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* block by padding necessary 0s
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*/
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if (x_len) {
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memcpy(tmp, x, x_len);
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xor_data(z, tmp);
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gcm_mult(ctx, z, z);
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}
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}
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/* Function to init AES GCM context to zero */
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void esp_aes_gcm_init( esp_gcm_context *ctx)
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{
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if (ctx == NULL) {
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return;
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}
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bzero(ctx, sizeof(esp_gcm_context));
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ctx->gcm_state = ESP_AES_GCM_STATE_INIT;
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}
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/* Function to clear AES-GCM context */
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void esp_aes_gcm_free( esp_gcm_context *ctx)
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{
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if (ctx == NULL) {
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return;
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}
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bzero(ctx, sizeof(esp_gcm_context));
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}
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/* Setup AES-GCM */
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int esp_aes_gcm_starts( esp_gcm_context *ctx,
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int mode,
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const unsigned char *iv,
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size_t iv_len )
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{
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/* IV is limited to 2^32 bits, so 2^29 bytes */
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/* IV is not allowed to be zero length */
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if ( iv_len == 0 ||
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( (uint32_t) iv_len ) >> 29 != 0 ) {
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return ( MBEDTLS_ERR_GCM_BAD_INPUT );
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}
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if (!ctx) {
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ESP_LOGE(TAG, "No AES context supplied");
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return -1;
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}
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if (!iv) {
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ESP_LOGE(TAG, "No IV supplied");
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return -1;
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}
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/* Initialize AES-GCM context */
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memset(ctx->ghash, 0, sizeof(ctx->ghash));
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ctx->data_len = 0;
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ctx->iv = iv;
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ctx->iv_len = iv_len;
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ctx->mode = mode;
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/* H and the lookup table are only generated once per ctx */
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if (ctx->gcm_state == ESP_AES_GCM_STATE_INIT) {
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/* Lock the AES engine to calculate ghash key H in hardware */
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esp_aes_acquire_hardware();
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ctx->aes_ctx.key_in_hardware = aes_hal_setkey(ctx->aes_ctx.key, ctx->aes_ctx.key_bytes, mode);
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aes_hal_mode_init(ESP_AES_BLOCK_MODE_GCM);
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aes_hal_gcm_calc_hash(ctx->H);
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esp_aes_release_hardware();
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gcm_gen_table(ctx);
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}
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ctx->gcm_state = ESP_AES_GCM_STATE_START;
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return ( 0 );
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}
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int esp_aes_gcm_update_ad( esp_gcm_context *ctx,
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const unsigned char *aad,
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size_t aad_len )
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{
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/* AD are limited to 2^32 bits, so 2^29 bytes */
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if ( ( (uint32_t) aad_len ) >> 29 != 0 ) {
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return ( MBEDTLS_ERR_GCM_BAD_INPUT );
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}
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if (!ctx) {
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ESP_LOGE(TAG, "No AES context supplied");
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return -1;
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}
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if ( (aad_len > 0) && !aad) {
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ESP_LOGE(TAG, "No aad supplied");
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return -1;
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}
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/* Initialize AES-GCM context */
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memset(ctx->ghash, 0, sizeof(ctx->ghash));
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ctx->data_len = 0;
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ctx->aad = aad;
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ctx->aad_len = aad_len;
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if (ctx->gcm_state != ESP_AES_GCM_STATE_START) {
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ESP_LOGE(TAG, "AES context in invalid state!");
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return -1;
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}
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/* Once H is obtained we need to derive J0 (Initial Counter Block) */
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esp_gcm_derive_J0(ctx);
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/* The initial counter block keeps updating during the esp_gcm_update call
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* however to calculate final authentication tag T we need original J0
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* so we make a copy here
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*/
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memcpy(ctx->ori_j0, ctx->J0, 16);
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esp_gcm_ghash(ctx, ctx->aad, ctx->aad_len, ctx->ghash);
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return ( 0 );
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}
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/* Perform AES-GCM operation */
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int esp_aes_gcm_update( esp_gcm_context *ctx,
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const unsigned char *input, size_t input_length,
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unsigned char *output, size_t output_size,
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size_t *output_length )
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{
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size_t nc_off = 0;
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uint8_t nonce_counter[AES_BLOCK_BYTES] = {0};
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uint8_t stream[AES_BLOCK_BYTES] = {0};
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if (!output_length) {
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ESP_LOGE(TAG, "No output length supplied");
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return -1;
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}
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*output_length = input_length;
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if (!ctx) {
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ESP_LOGE(TAG, "No GCM context supplied");
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return -1;
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}
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if (!input) {
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ESP_LOGE(TAG, "No input supplied");
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return -1;
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}
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if (!output) {
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ESP_LOGE(TAG, "No output supplied");
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return -1;
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}
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if ( output > input && (size_t) ( output - input ) < input_length ) {
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return ( MBEDTLS_ERR_GCM_BAD_INPUT );
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}
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/* If this is the first time esp_gcm_update is getting called
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* calculate GHASH on aad and preincrement the ICB
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*/
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if (ctx->gcm_state == ESP_AES_GCM_STATE_START) {
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/* Jo needs to be incremented first time, later the CTR
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* operation will auto update it
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*/
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increment32_j0(ctx, nonce_counter);
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ctx->gcm_state = ESP_AES_GCM_STATE_UPDATE;
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} else if (ctx->gcm_state == ESP_AES_GCM_STATE_UPDATE) {
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memcpy(nonce_counter, ctx->J0, AES_BLOCK_BYTES);
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}
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/* Perform intermediate GHASH on "encrypted" data during decryption */
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if (ctx->mode == ESP_AES_DECRYPT) {
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esp_gcm_ghash(ctx, input, input_length, ctx->ghash);
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}
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/* Output = GCTR(J0, Input): Encrypt/Decrypt the input */
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esp_aes_crypt_ctr(&ctx->aes_ctx, input_length, &nc_off, nonce_counter, stream, input, output);
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/* ICB gets auto incremented after GCTR operation here so update the context */
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memcpy(ctx->J0, nonce_counter, AES_BLOCK_BYTES);
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/* Keep updating the length counter for final tag calculation */
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ctx->data_len += input_length;
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/* Perform intermediate GHASH on "encrypted" data during encryption*/
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if (ctx->mode == ESP_AES_ENCRYPT) {
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esp_gcm_ghash(ctx, output, input_length, ctx->ghash);
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}
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return 0;
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}
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/* Function to read the tag value */
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int esp_aes_gcm_finish( esp_gcm_context *ctx,
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unsigned char *output, size_t output_size,
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size_t *output_length,
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unsigned char *tag, size_t tag_len )
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{
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size_t nc_off = 0;
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uint8_t len_block[AES_BLOCK_BYTES] = {0};
|
|
uint8_t stream[AES_BLOCK_BYTES] = {0};
|
|
|
|
if ( tag_len > 16 || tag_len < 4 ) {
|
|
return ( MBEDTLS_ERR_GCM_BAD_INPUT );
|
|
}
|
|
|
|
/* Calculate final GHASH on aad_len, data length */
|
|
ESP_PUT_BE64(len_block, ctx->aad_len * 8);
|
|
ESP_PUT_BE64(len_block + 8, ctx->data_len * 8);
|
|
esp_gcm_ghash(ctx, len_block, AES_BLOCK_BYTES, ctx->ghash);
|
|
|
|
/* Tag T = GCTR(J0, ) where T is truncated to tag_len */
|
|
esp_aes_crypt_ctr(&ctx->aes_ctx, tag_len, &nc_off, ctx->ori_j0, stream, ctx->ghash, tag);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Due to restrictions in the hardware (e.g. need to do the whole conversion in one go),
|
|
some combinations of inputs are not supported */
|
|
static bool esp_aes_gcm_input_support_hw_accel(size_t length, const unsigned char *aad, size_t aad_len,
|
|
const unsigned char *input, unsigned char *output, uint8_t *stream_in)
|
|
{
|
|
bool support_hw_accel = true;
|
|
|
|
if (aad_len > ESP_AES_GCM_AAD_MAX_BYTES) {
|
|
support_hw_accel = false;
|
|
} else if (!esp_ptr_dma_capable(aad) && aad_len > 0) {
|
|
/* aad in non internal DMA memory */
|
|
support_hw_accel = false;
|
|
} else if (!esp_ptr_dma_capable(input) && length > 0) {
|
|
/* input in non internal DMA memory */
|
|
support_hw_accel = false;
|
|
} else if (!esp_ptr_dma_capable(output) && length > 0) {
|
|
/* output in non internal DMA memory */
|
|
support_hw_accel = false;
|
|
} else if (!esp_ptr_dma_capable(stream_in)) {
|
|
/* Stream in (and therefor other descriptors and buffers that come from the stack)
|
|
in non internal DMA memory */
|
|
support_hw_accel = false;
|
|
} else if (length == 0) {
|
|
support_hw_accel = false;
|
|
}
|
|
|
|
|
|
return support_hw_accel;
|
|
}
|
|
|
|
static int esp_aes_gcm_crypt_and_tag_partial_hw( esp_gcm_context *ctx,
|
|
int mode,
|
|
size_t length,
|
|
const unsigned char *iv,
|
|
size_t iv_len,
|
|
const unsigned char *aad,
|
|
size_t aad_len,
|
|
const unsigned char *input,
|
|
unsigned char *output,
|
|
size_t tag_len,
|
|
unsigned char *tag )
|
|
{
|
|
int ret = 0;
|
|
size_t olen;
|
|
|
|
if ( ( ret = esp_aes_gcm_starts( ctx, mode, iv, iv_len ) ) != 0 ) {
|
|
return ( ret );
|
|
}
|
|
|
|
if ( ( ret = esp_aes_gcm_update_ad( ctx, aad, aad_len ) ) != 0 ) {
|
|
return ( ret );
|
|
}
|
|
|
|
if ( ( ret = esp_aes_gcm_update( ctx, input, length, output, 0, &olen ) ) != 0 ) {
|
|
return ( ret );
|
|
}
|
|
|
|
if ( ( ret = esp_aes_gcm_finish( ctx, output, 0, &olen, tag, tag_len ) ) != 0 ) {
|
|
return ( ret );
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
int esp_aes_gcm_crypt_and_tag( esp_gcm_context *ctx,
|
|
int mode,
|
|
size_t length,
|
|
const unsigned char *iv,
|
|
size_t iv_len,
|
|
const unsigned char *aad,
|
|
size_t aad_len,
|
|
const unsigned char *input,
|
|
unsigned char *output,
|
|
size_t tag_len,
|
|
unsigned char *tag )
|
|
{
|
|
int ret;
|
|
lldesc_t aad_desc[2] = {};
|
|
lldesc_t *aad_head_desc = NULL;
|
|
size_t remainder_bit;
|
|
uint8_t stream_in[AES_BLOCK_BYTES] = {};
|
|
unsigned stream_bytes = aad_len % AES_BLOCK_BYTES; // bytes which aren't in a full block
|
|
unsigned block_bytes = aad_len - stream_bytes; // bytes which are in a full block
|
|
|
|
/* Due to hardware limition only certain cases are fully supported in HW */
|
|
if (!esp_aes_gcm_input_support_hw_accel(length, aad, aad_len, input, output, stream_in)) {
|
|
return esp_aes_gcm_crypt_and_tag_partial_hw(ctx, mode, length, iv, iv_len, aad, aad_len, input, output, tag_len, tag);
|
|
}
|
|
|
|
/* Limit aad len to a single DMA descriptor to simplify DMA handling
|
|
In practice, e.g. with mbedtls the length of aad will always be short
|
|
*/
|
|
if (aad_len > LLDESC_MAX_NUM_PER_DESC) {
|
|
return -1;
|
|
}
|
|
/* IV and AD are limited to 2^32 bits, so 2^29 bytes */
|
|
/* IV is not allowed to be zero length */
|
|
if ( iv_len == 0 ||
|
|
( (uint32_t) iv_len ) >> 29 != 0 ||
|
|
( (uint32_t) aad_len ) >> 29 != 0 ) {
|
|
return ( MBEDTLS_ERR_GCM_BAD_INPUT );
|
|
}
|
|
|
|
if (!ctx) {
|
|
ESP_LOGE(TAG, "No AES context supplied");
|
|
return -1;
|
|
}
|
|
|
|
if (!iv) {
|
|
ESP_LOGE(TAG, "No IV supplied");
|
|
return -1;
|
|
}
|
|
|
|
if ( (aad_len > 0) && !aad) {
|
|
ESP_LOGE(TAG, "No aad supplied");
|
|
return -1;
|
|
}
|
|
|
|
/* Initialize AES-GCM context */
|
|
memset(ctx->ghash, 0, sizeof(ctx->ghash));
|
|
ctx->data_len = 0;
|
|
|
|
ctx->iv = iv;
|
|
ctx->iv_len = iv_len;
|
|
ctx->aad = aad;
|
|
ctx->aad_len = aad_len;
|
|
ctx->mode = mode;
|
|
|
|
esp_aes_acquire_hardware();
|
|
ctx->aes_ctx.key_in_hardware = 0;
|
|
ctx->aes_ctx.key_in_hardware = aes_hal_setkey(ctx->aes_ctx.key, ctx->aes_ctx.key_bytes, mode);
|
|
|
|
if (block_bytes > 0) {
|
|
aad_desc[0].length = block_bytes;
|
|
aad_desc[0].size = block_bytes;
|
|
aad_desc[0].owner = 1;
|
|
aad_desc[0].buf = aad;
|
|
}
|
|
|
|
if (stream_bytes > 0) {
|
|
memcpy(stream_in, aad + block_bytes, stream_bytes);
|
|
|
|
aad_desc[0].empty = (uint32_t)&aad_desc[1];
|
|
aad_desc[1].length = AES_BLOCK_BYTES;
|
|
aad_desc[1].size = AES_BLOCK_BYTES;
|
|
aad_desc[1].owner = 1;
|
|
aad_desc[1].buf = stream_in;
|
|
}
|
|
|
|
if (block_bytes > 0) {
|
|
aad_head_desc = &aad_desc[0];
|
|
} else if (stream_bytes > 0) {
|
|
aad_head_desc = &aad_desc[1];
|
|
}
|
|
|
|
aes_hal_mode_init(ESP_AES_BLOCK_MODE_GCM);
|
|
|
|
/* See TRM GCM chapter for description of this calculation */
|
|
remainder_bit = (8 * length) % 128;
|
|
aes_hal_gcm_init( (aad_len + AES_BLOCK_BYTES - 1) / AES_BLOCK_BYTES, remainder_bit);
|
|
aes_hal_gcm_calc_hash(ctx->H);
|
|
|
|
gcm_gen_table(ctx);
|
|
esp_gcm_derive_J0(ctx);
|
|
|
|
aes_hal_gcm_set_j0(ctx->J0);
|
|
|
|
ret = esp_aes_process_dma_gcm(&ctx->aes_ctx, input, output, length, aad_head_desc, aad_len);
|
|
|
|
aes_hal_gcm_read_tag(tag, tag_len);
|
|
|
|
esp_aes_release_hardware();
|
|
|
|
return ( ret );
|
|
}
|
|
|
|
|
|
int esp_aes_gcm_auth_decrypt( esp_gcm_context *ctx,
|
|
size_t length,
|
|
const unsigned char *iv,
|
|
size_t iv_len,
|
|
const unsigned char *aad,
|
|
size_t aad_len,
|
|
const unsigned char *tag,
|
|
size_t tag_len,
|
|
const unsigned char *input,
|
|
unsigned char *output )
|
|
{
|
|
int ret;
|
|
unsigned char check_tag[16];
|
|
size_t i;
|
|
int diff;
|
|
|
|
if ( ( ret = esp_aes_gcm_crypt_and_tag( ctx, ESP_AES_DECRYPT, length,
|
|
iv, iv_len, aad, aad_len,
|
|
input, output, tag_len, check_tag ) ) != 0 ) {
|
|
return ( ret );
|
|
}
|
|
|
|
/* Check tag in "constant-time" */
|
|
for ( diff = 0, i = 0; i < tag_len; i++ ) {
|
|
diff |= tag[i] ^ check_tag[i];
|
|
}
|
|
|
|
if ( diff != 0 ) {
|
|
bzero( output, length );
|
|
return ( MBEDTLS_ERR_GCM_AUTH_FAILED );
|
|
}
|
|
|
|
return ( 0 );
|
|
}
|
|
|
|
#endif //SOC_AES_SUPPORT_GCM
|